The Roman invasion and occupation of Gallaecia around
50 AD was accompanied with the adoption of the Latin language by
some Gallaecians, however Latin inscriptions, spanning 50 AD to
the 17th century AD, made on the Late Iron Age Warrior Statues of
Gallecia contain some embedded Gallaic Celtic words indicating survival
in some sense of the Gallaic Celtic language for a considerable
time after Roman conquest (González-Ruibal, 2004, Prósper
2002, 2005).
Ancient Greek historian Herodotus in his "The
History of Herodotus" Book 2 verse 34 written in 440 BC states
that: "The Celts live beyond the pillars of Hercules [now Gibraltar],
and border on the Cynesians, who dwell at the extreme west of Europe."
This is repeated in Book 4 verse 48. (Herodotus 440 BC). The Cynesians
lived between the rier Anas (now called Guadiana) and the Sacrum
Promontorium (Sagres), so the location for people called the 'Celts'
(KELTOI in Greek) is on or near the stretch of Coast between the
Straits of Gibraltar and the present day Spanish-Portuguese border.
Neither passage in the Histories states or implies that the KELTOI
were newcomers to the south-west Iberian peninsula in the 5th. century
BC. It is probable that these south-western KELTOI spoke a Celtic
language as their name implies. It is also clear-cut linguistically
that the group name of the neighbouring Cynesians to the west in
Portugal (called KUNETES in Greek, Latinised to Cynetes, also Conii)
is derived from the Celtic word for 'hound', figuratively 'hero'.
(Koch 2011 page 29).
Large and extensive amounts of Hallstatt coarse stamped
pottery dated to around 800 BC have been found in Portugal and Spain,
in particular South-west Portugal and the main river valleys and
highlands of Andalusia in Spain indicating a dense Celtic settlement
which would become the basis for the Tartessian civilisation; Galicia
and Asturias similarly. This archaeological evidence for dense Celtic
settlement in Portugal and Spain is backed up by the writings of
ancient historians such as Ephorus and Herodotus who mention such
settlements specifically "...as.far as Cadiz".
However, a number of indicators are telling us that Celtic settlement
may be much more ancient than that in this region. There are ancient
Celtic placenames in NW Africa that appear to be only explicable
by the distribution of the Bell Beaker culture. The most ancient
Bell Beakers are the Maritime Bell Beakers originating around the
Tagus River estuary in Portugal around 2,900 BC and spreading rapidly
by migration to other parts of Europe and North Africa by sea and
river. Ancient DNA extracted from Bell Beaker people's graves have
shown that the males carry the Y-DNA
haplogroup R1b M-269 mutation thought to mark the spread of Celtic
populations. Genetic
studies of the present population of Huelva near Seville in southern
Spain have suggested that the area was more likely the source area
for other populations of Western Europe rather than being an oultier.
On the map below the close fit between Bell Beaker culture and Celtic
language distribution is shown. The epicentre origin of the Beaker
culture is clearly shown around the Tagus estuary in Portugal as
is the Gallicia-Asturias-North Portugal Gallaecian and Meseta Spain
Celtiberian area and the nucleus of the Tartessian civilization
as major nodes
of occurrence of International Beaker styles. This fit becomes
even much closer when ancient Celtic place and group names indicating
what are thought to be ancient Celtic substratum populations are
factored in such as the Saguntum on the Mediterranean coast north
of Valencia; Ebora, Segida, Saguntia and Ebora in the Tartessian
zone south and east of the Guadalquivir River; and Rutubis, Uobrix,
Uerbikes and Uerueis in northern and Atlantic Morocco (Koch 2011).

How the
Celtic Languages developed and spread
Bards of the Cornish Gorsedd, Joy (Cherya) and Chris (Kevrenor)
Dunkerley, compiled this research report published in "The
Newsletter of the Cornish Association of New South Wales",
Australia (No. 348, Circulation 110, ISSN 1321-3199, December 2013-January
2014) and reproduced here with their permission. This is how they
understand it from the evidence at hand. Please see "Celtic
from the West" and "Celtic
from the West 2" for more details on this line of thought.
Another interesting paper along these lines is
Celtic Origins: Iberian Connections by Seamus Hamill-Keays.